Oxidation of organic compounds, which, like reduction, is one of the most important functional group conversion reactions in the field of organic synthesis, is extremely useful in reactions for synthesizing functional compounds such as medicines and dyes.
For example, a 2-aryl benzoxazole skeleton, which is included in the basic skeletons of medicines, such as anti-inflammatory agents and anticancer agents, must have conventionally been synthesized from a 2-aminophenol derivative and a benzaldehyde derivative using a stoichiometric or excessive amount of oxidizing agent which tends to load to the environment, such as barium permanganate, lead tetraacetate and DDQ.
A carbonyl compound produced through oxidation of and corresponding to an alkylarene, which is a starting material to important compounds because of the capability of being converted easily into compounds with various types of functional groups, has conventionally needed use of a stoichiometric amount of oxidizing agent such as manganese dioxide, selenium dioxide and periodic acid. Although a method using oxygen in the air has also been researched, it needs N-hydroxyphthalimide, ruthenium complexes, cobalt-Schiff base complexes or the like as a catalyst.
A method for producing 4-oxyisophorone by oxidizing β-isophorone using oxygen or oxygen-containing gas in the presence of activated carbon and a nitrogen-containing heterocyclic base instead of using such toxic catalysts has been proposed (Japanese Unexamined Patent Application Publication No. 11-49717). Regarding the activated carbon, however, only ones with specific surface areas ranging widely from 30 to 2000 m2/g are disclosed. Its working examples refer only to “activated carbon from coconut shell for chromatography” and do not use any special ones. The reactions require the presence of a specific type of nitrogen-containing heterocyclic base and no particular references are made to catalytic actions on other reaction substrates.